Total timing advance suggestions

[AlanCasida]

Thanks a lot for all the input, guys. I really appreciate it. Goodness knows I need all the help I can get!!

[KeiserMustang]

I'm in Indy this weekend on the second time out with the new 482 TFS engine. Haven't done as much testing as I want yet but I can say this engine shows signs of dropping off as the timing approaches 30 degrees BTDC...best pass at Norwalk was at 25 advance and I was intentionally trying to slow it down....

Really challenging my thinking here...the 428 with Edelbrock heads and10:1 comp wanted 38 adv.

Is it right to think this combination my legitimately run best around in the mid 20's for total timing?

Its 12.15:1 comp, .040" quench, TFS heads.

[blykins]

May wanna check your balancer marks and verify TDC. 

[Thumperbird]

Edelbrock's on my stroker but just went from 18 to 20 initial and as Cammer FE said, makes a ton of difference down low in idle and pull (smoothness and launch at least).  Had been hesitant to go over 18 and allow in gear rpm's up over say 850 but decided to try it as I had a free evening, 20 initial, ~37 total, 900 rpm's in gear, tweaked A/F and very solid off the line and throughout.  All in timing is set a little slower than some others I suspect due to very heavy car. 

[KeiserMustang]

May wanna check your balancer marks and verify TDC.

I did just that during assembly. I have a new ATI balancer and set my timing pointer perfect to TDC. Have checked timing with two different lights, both agreed.

At 31 total adv it started to develop a slight miss down track
At 23 total, a hiccup coming off the starting line.

[plovett]

My Edelbrocks liked around 37 degrees best on the dyno.   Surely the Trick Flow heads will need less.  That doesn't tell you an exact number, but it tells you that you will almost certainly want less than 37 degrees. 

I think the octane of the fuel, and of course the compression ratio, makes a difference, too.  I have been told I am wrong about that before.  Could be.  Also cam timing...… 

…..and vehicle weight and gearing, and air temperature.  …..and altitude....   and stall speed...…    and...…. LOL!

JMO,

paulie

[My427stang]

It's all about flame travel, all ignition advance does is allow the air/fuel mixture to do a complete burn when it's the proper time when you are at a given RPM

- Big chamber, takes longer, more advance
- Sloppy chamber, not churned well - more advance
- Mixture lean - more advance
- Less or mismatching squish pad churning things - more advance
- Big dome, usually more advance, but sometimes just crappy burn
- Lots of overlap - poorly burning mixture,  wants more advance until things get efficient with overlap

Keep in mind, this is what then engine would want for making power, not what it can handle

- Big chamber, loose quench, lean mixture WANTS advance, but may not be able to handle it.  That's why we try to keep things tight.

Should have some good data in November, doing a 10.25:1, Trick Flow headed 461, .041 quench, with 64 degrees overlap, estimate is a peak around 6200 RPM.  Nice clean chamber and piston, should end up around 16 in vacuum at idle.  Shouldn't need a lot of advance. 

TFS heads certainly need less than an Edelbrock unless someone tried hard to make it less efficient LOL if for no other reason, the chamber is 5-6 cc smaller and replaced with quench pad. 

Brent has built a few of these now, if build is anything like his, just listen to him on where to start for total.  I intend to start this one at 32 on the dyno and experiment from there

[plovett]

Keep in mind, this is what then engine would want for making power, not what it can handle

You are absolutely correct.  I was looking at it from the other side.  What it can handle.   And even in a sub-optimal situation you might be able to get the same total timing, with a different curve.  I know you know this.  Just working my jaw. 

paulie

[plovett]

Brent has built a few of these now, if build is anything like his, just listen to him on where to start for total.  I intend to start this one at 32 on the dyno and experiment from there

This is true, too.  If Brent knows where the typical build works best within 2 degrees or so, you are already 99% there.

JMO,

paulie

[blykins]

Mine have generally wanted 32-34 degrees. 

Sometimes you see a head make bigger power with less timing on the dyno but it’s lazier in the car.

Any type of miss or cut out would not be timing relayed.  Maybe fuel, etc.

[shady]

maybe check rotor phasing?

[Yellow Truck]

No expert, but at 3,500 feet my 445 with BBM heads liked 18 initial and 34 total, moved to sea level and it likes 24 initial and 34 total. I did check my timing marks with a piston stop so I know my TDC mark is about 2 degrees out and those numbers take the error into consideration. Had to change the stop position on the distributor to bring total down, but it wasn't complaining about total at nearly 40. Having said that we only saw 40 while testing without load and once we were sure it wanted 24 initial we pulled the distributor and changed the stop position.

I don't know if it is normal for an engine to like more advance when it is getting more oxygen, but mine seemed to. Of course, I could have been too timid with the advance at 3,500 feet, but it seemed to labour more at sea level than at altitude with 18 degrees of advance. Was much easier to dial in the carb with the initial at 24.

I'm not running vacuum advance at present.